Will_paginate - NoMethodError - 未定义的方法`total_pages n＃39; ActiveRecord关联

Question

我正在尝试对我的项目模型进行分页（will_paginate gem），该模型有很多注释（acts_as_commentable_with_threading gem）：

@root_comments = @project.root_comments.paginate(:per_page => 2, :page => params[:discussions_page])

堆栈追踪：

NoMethodError - undefined method `total_pages' for #<Comment::ActiveRecord_AssociationRelation:0x007fa183d77ce8>:
  activerecord (4.1.4) lib/active_record/relation/delegation.rb:136:in `method_missing'
  activerecord (4.1.4) lib/active_record/relation/delegation.rb:99:in `method_missing'
  will_paginate (3.0.5) lib/will_paginate/view_helpers.rb:73:in `will_paginate'
  will_paginate (3.0.5) lib/will_paginate/view_helpers/action_view.rb:33:in `will_paginate'

知道我为什么会收到错误？

<%= will_paginate @root_comments,:param_name => 'discussions_page', renderer: BootstrapPagination::Rails %>